WASHINGTON — The US Senate moved one step closer Wednesday to extending — just barely — a 51-year streak of sending the president an annual Pentagon policy bill.

The upper chamber voted to end debate on the House-passed national defense authorization act (NDAA) that would, if approved later this week, clear the Pentagon to spend $607 billion in fiscal 2014. It authorizes $527 billion in base funding and $80 billion for America’s global conflicts.

The compromise measure was pieced together during Congress’ Thanksgiving recess by House and Senate Armed Services Committee leaders and top aides. No amendments were allowed on either the House or Senate floor, raising the ire of Senate Republicans who say Majority Leader Sen. Harry Reid, D-Nev., too often refuses their amendments on all bills.

Still, enough Republicans viewed the military authorization bill as too important to kill for the second time in a month over the amendments flap.

The chamber dispensed with drama briefly expected last week, easily voting to end debate, 71-29.

One senior SASC aide said it is “likely the final vote will be Thursday.” The exact timing of the up-or-down NDAA vote remains in flux.

With cloture invoked, a 30-hour clock is running. After it expires, the chamber will hold a final vote on the defense bill. Fifty-one votes are needed to pass it, and none of the chamber’s 53 Democrats has signaled a vote against it, meaning it’s almost certainly headed to President Barack Obama’s desk.

Whether that will happen on Thursday or Friday is unclear.

“It depends if both sides yield back their time post-cloture,” the senior SASC aide said, referring to Senate rules that allow both parties to take time off the cloture clock.

Another Senate aide said if the chamber were to remain in session Thursday to allow a full 30-hour NDAA cloture clock to expire, a final vote likely would occur around 11 p.m. Alternatively, if neither side yields time, the chamber could vote Friday morning.

Of course, with a lengthy holiday recess just hours away and with Reid planning votes on a slew of nominations after the NDAA is cleared, eager-to-leave senators may choose to green-light their leaders to move to a final vote much sooner on Thursday. ■